Yue Zhou , Yung Sung Cheng

  • Lovelace Respiratory Research Institute, 2425 Ridgecrest SE, Albuquerque, NM, 87108, USA

Received: June 9, 2015
Revised: July 29, 2015
Accepted: July 30, 2015
Download Citation: ||https://doi.org/10.4209/aaqr.2015.06.0399  

  • Download: PDF

Cite this article:
Zhou, Y. and Cheng, Y.S. (2016). Evaluation of N95 Filtering Facepiece Respirators Challenged with Engineered Nanoparticles. Aerosol Air Qual. Res. 16: 212-220. https://doi.org/10.4209/aaqr.2015.06.0399


  • NIOSH certified N95 respirators were evaluated for engineered nanoparticles.
  • Penetrations of engineered nanoparticles were higher than that of NaCl.
  • Engineered nanoparticles often exceeded 5% near the MPPS at high flow rates.
  • Penetrations increased after removal of respirator electrostatic charges. 



NIOSH-certified respirators, including N95 respirators, are recommended when engineering and administrative controls do not adequately prevent exposures to airborne nanomaterials. Laboratory evaluations of filtering efficiency using standard test aerosols have been reported in the literature, but there is no information on penetration of engineered nanoparticles (1–100 nm) for N95 filtering facepiece respirators (FFR). This project evaluated the performance of two manufacturers’ N95 FFR filters challenged with engineered nanoparticle aerosols containing metal oxides (such as TiO2) and carbon (such as fullerenes and nanotubes) in contrast with a sodium chloride (NaCl) aerosol at flow rates of 30, 85, and 130 L min–1. For new respirator filters in general, NaCl aerosol penetration was less than 5% and the most penetrating particle size occurred at 40 nm. Overall penetration of the engineered nanoparticle aerosols exceeded 5% and was often greater than 5% at and near the most penetrating particle size (MPPS), which occurred at a larger particle size range (90–150 nm). For respirators treated with isopropanol in which the electrostatic force was removed, penetration of NaCl and engineered nanoparticles increased substantially and the MPPS increased to 150 nm for both types of aerosols. Our results indicated that a possible reason for higher maximum penetrations and shift of MPPS observed for these engineered nanoparticles in the new respirators was related to electrostatic collection processes.

Keywords: N95 filter; Aerosol penetration; Electret filter; Engineered nanoparticles

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